We utilize two existing results for the proof of Theorem
REF . The first result is
[1]}, which is restated as Theorem
REF  below. This result implies that upper bounds for
the metric entropy of \(\mathcal {D}_m\)  can be obtained by appropriate
lower bounds on the small ball probability of integrated Brownian
sheet. The second result is [2]}, which is
restated as Theorem REF  below. This result helps us
connect the small ball probability of integrated Brownian sheet to
that of the Brownian sheet whose lower bounds are quite well
studied.
